Electronic musical instrument



Feb. 9, 1960 R. H. PETERSON 2,924,137

ELECTRONIC MUSICAL INSTRUMENT Filed Feb. 20, 1956 3 Sheets-Sheet 2 1% J39 NORMALE m Q 1% v DOLCE w 1410 140 M u TO m P IAN G E R E I 02/18 rel Z27 r EacizardA/Peizraaa United States Patent ELECTRONIC MUSICAL INSTRUMENT Richard H. Peterson, Oaklawn, Ill.

Application February 20, 1956, Serial No. 566,446

8 Claims. (Cl. 84--1.26)

producing unit according to the invention;

Figure 2 is a front elevation of an interrupter;

Figure 3 is a sectional view of the interrupter of Figure 2 on line 33 of Figures 2 and 4;

Figure 4 is a plan view of the interrupter, as on line 44 of Figures 2 and 3;

Figure 5 is a partial wiring diagram indicating the relation of the novel modification to the conventional keyboards;

Figure 6 is a diagram indicating the nature of the time sequences secured with different adjustment of the timer;

Figure 7 is a schematic wiring diagram indicating equipment for obtaining a wider variety of elfects; and

Figure 8 is a diagram indicating the nature of the time sequences of decay obtainable with an instrument according to Figure 7.

Referring first to Figure 1, I have illustrated a conventional Hartley oscillator 10 having a tuned circuit, of highly constant frequency, including the inductance 12 and capacitor 14. The activating triode is illustrated as a tube 16 with a cathode 18, grid 20, and plate 22. During playing of the instrument, the cathode 18 is kept continuously operative by conventional heating means. There is one such oscillator for each pitch to be produced by the instrument, and each oscillator has its plate operatively connected with an individual D.C. conductor 24 adapted to receive potential from a conventional source 42 through switches 26 and 28 controlled by keys 30 and 32 (see Figure 3) manipulated by the fingers of the player, to start and stop the tone delivery.

The switch 26 activates the conductor 24 directly, through the resistor 33. The capacitor 34 combines with theresistor 33 to constitute an R-C time delay circuit which controls the timing of the inception, or attack, of the tone produced. The switch 28 activates the same conductor 24 through the same protective resistor 33,

is subsequently opened, the energy stored in capacitor 34 has to discharge through the tube 16 and part of the inductance 12, to ground at 46. This discharge determines the decay of the tone when the switch-26 is opened. However, if the tone was sounded with switch 28, or if switch 28 was closed while the tone was being sounded with switch 26, the much larger energy stored in capacitor 38 will also have to discharge through the same path, and the decay of the note will be correspondingly prolonged.

When the switches 26 and 28 receive energy direct from the source 42, playing the instrument as above outlined with key 32 and switch 28 will cause it to simulate a bell, or a piano with the sustaining pedal held down, but playing it with key 30 and switch 26 will give the relatively abrupt decay characteristic of a piano with the sustaining pedal left up.

I have provided additional means for automatic repeated interruption of the DC. activating circuit to enable the operator to simulate the music produced with a Xylophone, banjo, mandolin, or the like.

As illustrated, the interrupter 48 is connected so that the operator can interpolate it between the source 42 and either or both of the switches 26 and 28. For this purpose the switch 28 is connected through conductor 50 and contact 52 of the interrupter, and then through conductor 54 to the interrupter switch 56, and through conductor 58 back to the source 42. In Figure 1, switch 56 is shown in a position to render the interrupter operative. By turning the switch counterclockwise to engage the contact 60, the interrupter is taken out of the circuit and a direct connection established to switch 28.

Similarly, switch 26 is connected through conductor 60 to contact 62 of the interrupter, and from the interrupter through conductor 64 to switch 66, and through the same conductor 58 to the source 42. Switch 66 is also shown in position to render the interrupter operative, but rotation of the switch in a clockwise direction to engage contact 60 will take the interrupter out of the circuit and establish a direct D.C. connection to switch 26.

It will be obvious that the interrupter can be either electronic or mechanical. In Figures 2, 3, and 4 I have illustrated a mechanical interrupter. The supporting panel 70 has a bottom shelf 72 supporting a miniature motor 74 connected through a speed reducer 76 to the eccentric 78. The pitman S0 rises between the relatively movable contact arm 82 co-operating with the contact 52, and contact arm 84 co-operating with the contact 62. The cross-piece 86 overlies both contact arms 82 and 84, and the connection may be adjusted by means of the adjusting nut 88.

The contact arms 82 and 84 are resilient and terminate in upwardly directed extensions 90 and 92 clamped between insulating blocks 94 set in a U-shaped metal holder 96, which may be integral with the panel 70. An insulating spacer block 98 braces the arms 82 and 84, and keeps them in good alignment. The contact arms 52 and 62 are also flexible but materially less so than the arms 82 and 84. They terminate in upwardly directed extensions 1% and 182 clamped between insulating blocks 94 in the U-shaped receiver 104 at the upper left corner of the panel 70. It will be obvious that, with the parts properly adjusted, actuation of the motor 74 will raise and lower the arms 82. and 84, and open and close the effective connection between the source 42 and the switches 26 and 28, with the frequency depending on the speed of the motor and the time cycle depending on the adjustment of the parts. But this will make no music except when the operator closes the switch 26 or the switch 28 to continue the connection through to the tonegenerating unit.

Means are provided for varying both the speed of the motor 74 and the nature of the contact cycle. From one power line the circuit is through switch contact (see Figure 2), a portion of control resistor 112, conductor 114, and the motor 74 to the other line 108. The switch 110 may be slidably mounted on the shelf 116 where the operator can slide it back and forth to vary the speed of the motor. Conveniently, switches 56 and '66 maybe mounted on the same shelf close beside the adjusting button 118 for the switch 118.

To vary the portion of the cycle during which the contacts 52 and 62 will remain closed, I provide a ten- :SiOl] riser 120 carrying a cross-piece 122 underlying the contacts '52 and 62. The upper end of the riser 120 is connected to the short arm 124 of a bell crank lever having a long arm 126. The long arm 126 extends up- -ward through a slot 128 in the shelf 116 and carries a pointer 130. The arm 126 and pointer 136 may be .frictionally held in adjusted position by suitable means such as felting 132 having a light friction engagement lwiththe arm 126.

It will be apparent that raising and lowering the riser 120 will increase or decrease that portion of the time ,cycle represented by one revolution of the eccentric 78, during which the circuit will be closed. For convenience in discussing the acoustics involved, Figure 6 indicates five .diiferent conditions of adjustment for the contacts 52 .and '62. The lowest position of the contacts will produce the uppermost curve of Figure 6, indicating very :short closure periods at 134 amounting to about onetwelveth of the total time cycle. This condition is identifiable by the indicia Tint. The next condition of adjustment is identifiable as Normals. In this condition the contact periods 136 are about one-eighth of the total time cycle. Similarly, the next adjustment identifiable as .Dolce has longer contact periods 138; the

next condition Mute has longer contact periods 140 amounting to almost one-half the time cycle, and the last condition identifiable as Piangere has contact periods 142 amounting tomore than one-half the cycle.

With the attack of the tone generator adjusted so that it will build up to full intensity during the time interval represented by the contact period 136, thatcondition of adjustment will generate the normal tone quality for which the generating unit is designed. This may be any .of the tone qualities identified in US. Patent 2,649,006, issued August 18, 1953, or such other acoustical tone qualitiesas may be desired.

During the attack period of such a tone-generating unit the higher frequency overtones appear more quickly than the fundamental frequency, and if it takes the unit the entirety of time interval 136 to build its fundamental to full intensity, the much shorter time interval 134 will build the overtones to full intensity and come .to an end before the fundamental has risen to more than about onehalf its normal relative intensity. This will produce the tinny or tintinnabulating quality characteristic of a mandolin or similar instrument when the plectrum is shifted close to the bridge, commonly only about one-half as far from the bridge as the normal position.

It is well known that shifting the plectrum abnormally away from the bridge is also possible, even to a position substantially in the middle of the free length of the vibrating string, although the extreme central position requires great delicacy of touch for effectiveness. Such shifting away from the bridge materially reduces the higher overtones in playing such an instrument with a plectrum. The time interval 138 is long enough to build thefundamental to full intensity and hold it there for some time, and will produce a softer tone quality closely resembling the softer tone quality produced by striking with the plectrum at a point abnormally far from the bridge.

Similarly, the time interval identified as Muto will bear a resemblance to that relatively difiicult plectrum the frequency of plucking with an ordinary plectrum. I'prefer to provide an adjustment at the extremelyslow end, slow enough to permit a skillful and experienced player to manipulate the keys St) or 32 in synchromsm with the rotations of the eccentric 78, and perform staccato runs or arpeggios with just one impact for each note, but this will be an exceptional and unusual use of the instrument. The common use will be with the adjustment labeled Normale corresponding to the common trill frequency in mandolin play. This frequency can be reduced about twenty-five percent or increased about fifty percent by the player at will, corresponding to the positions identified as Lento, Presto, and Agrtato. The final condition identified as litter may be a frequency that is probably higher than the human hand can achieve with an ordinary plectrum and will be used for effects that Will be bizarre, if not perhaps better called crazy. It is possible to adjust the inertia of the moving parts of the mechanical interrupter so that whe n the motor is operatingat Jitter speed, their own inertia will give them an erratic jumping action in add1tion to the normal movement corresponding to the position of the eccentric 78. The cracked quaver of a senile voice can be closely approximated in this way.

In the embodiment of Figure 7 the same prolonged decay is obtained by the charging of the large capacitor, ratherthan the discharging. This is advantageous when the large capacitor is an electrolytic capacitor because the capacitor can remain normally charged. The key sw tches 144 may be associated with keys 30, and the key switches 146 with keys 32. When reiterating is desired, switch 148 is left open, and keys 30 will deliver interrupted activating DC. voltage through the contacts 150 of the interrupter. If reiteration is desired from keys 32, switch 152 is left open, and contacts 154 in the interrupter will deliver reiterated potential to switches 146.

The percussion effect is available only on keys 31 1, which actuate switches 144. The large capacitor 156 IS electrolytic, and is normally in a charged condition be cause of potential from source 42 coming constantly through switch 148 or frequently through contacts 150. In either instance, the current comes through conductor 158 and resistor 160 to one terminal of the capacitor 156. The other terminal is returned to ground through resistor 159.

When the key switch'144 closes, the capacitor 156 is completely discharged through conductor 169, the closed contacts 162 of the percussion cut-out control lever 164, conductors 171, 188 and 168 to switch 144, conductors 166 and 158 back to resistor 160 and capacitor 156. When the switch 144 is subsequently opened, the capacitor 156 must charge again in the circuit consisting of conductors 166 and 158, resistor 160, capacitor 156, conductor 169, contacts 162, conductors 171 and 188, rectifier 170, conductor 172, resistors 174 and 176, conductor 24, tube 16, and inductance 12 to ground at 46. Resistors 174, 176, tube 16 and inductance 12 are in parallel with resistor 159 during this charging, but resistor 159 has much higher resistance than the other branch of the circuit. This provides a continued supply of energy to keep the tube active and the generating" unit oscillating for a length of time dependent on the capacity of the capacitor 156.

Referring to the diagram of Figure 8, I have indicated time onthe horizontal axis with a maximum decay period of five seconds. The dotted line 178 indicates the relatively low potential at which the tube 16 will break down and the circuit will stop oscillating. The sustained vol- .ume of sound is indicated by the horizontal line 180, and when the circuit is manipulated as last described, the long deeply curved line 182 represents a close approximation to the rate at which 'the volume of sound will decrease during the decay period.

Means are provided underthe control of the player for ,causingthe decay to take place morerapidly. The

player-controlled adjustment lever 184 may be rotated counterclockwise from the position shown in the drawings to close contacts 186 and connect the negative side of the capacitor 156 to ground through conductor 188, contacts 186, and resistor 190. With the contacts 186 closed, the additional path to ground through resistor 190 increases the rate of charge and decay when the switch 144 is opened, and shortens the decay period. When the player-controlled contacts 186 are closed, the decay will be of the type indicated by full line 192 on Figure 8. The duration of theentire decay period is about cut in half, and the rate of decay during the period is much is so rapid that the curvature of line 200 is imperceptible.

These differences have their counterparts in the psychology of the listener. With a decay according to curve 182, the effect may be similar to that of an organ harp or vibra-harp. When the tone decays along line 200, the effect resembles that of a glockenspiel.

As in the parent application, Serial Number 503,104, filed April 22, 1955, the signal from the oscillator may be transmitted directly through resistor 202 to bus 204, which collects the signal from all the oscillators that are functioning and delivers it through the volume selector control 206 to the output bus 298, from which it goes through a conventional amplifier 210 and a conventional loud-speaker 212. Coupling units 214 and 216 may correspond to those described in detail in the parent application, and may change either the volume or the wave shape of the signal, or both, as desired. They receive the same signal from the oscillator through condoctors 218 and 220, but are inoperative unless they receive activating DC. potential through conductors 222 and 224 respectively. When couplings 214 are employed,

the modified oscillations from all the 214 couplings are assembled by bus bar 226 and transmitted through volume control 228 to the output bus bar 208. Similarly, when couplings 216 are operative, their output signals are assembled on collecting bus bar 230 and transmitted to delivery bus bar 208 through volume control 232.

Means are provided for selectively connecting all the couplings 214 or all the couplings 216 either to the switches 146 from which they can receive continuous or reiterated signal, or to the switches 144 from which they can receive signal that is either continuous or reiterated, and either percussion or not depending on the players adjustment of the stops actuating control levers 164, 184, and 196. I have illustrated a similar multiple contact control lever 234 in neutral position, so that coupling unit 214 does not function. Conductor 222 from coupling unit 214 leads to a double contact on control lever 234, and it will be obvious that displacement of the control lever clockwise will move the central contact up and connect coupling unit 214 through conductor 236 to conductor 172 controlled by switches 146. Similarly, counterclockwise displacement of control lever 234 will move the contact down and connect it to wire 188, so that percussion quality can be given to the signal from coupling unit 214.

Coupling unit 216 is controlled identically through player-controlled lever 238. While I have only illustrated two coupling units, it will be obvious that an indefinite number of similar coupling units can be provided in a more complete instrument, by mere addition of the coupling units and duplication of the control levers.

The normal attack, when activating potential is initially delivered, depends on the time constant of'capacitor 34 and the resistors 174 and 176. For certain bizarre efiects with an attack that verges on an explosive effect, it is necessary to have a much more abrupt attack. I have illustrated an operator-controlled multiple switch lever 240 projecting upward through the panel 116, and conductors 242 and 244 arranged to bypass or short circuit resistor 174, but not resistor 176. It will be obvious that rotation of the control stop 240 counterclockwise will close this short circuit and give the abrupt attack just mentioned.

Others may readily adapt the invention for use under various conditions of service by employing one or more of the novel features disclosed or equivalents thereof. As at present advised with respect to the apparent scope of my invention, I desire to claim the following subject matter:

1. In an electronic organ, in combination: an audiofrequency oscillator having the frequency of a musical note to be produced; loud speaker means for translating the vibrations of said oscillator into sound waves; said oscillator having a first and a second terminal; a first and a second key switch for delivering energizing voltage to sound said oscillator; a first circuit completed by said first key switch through said first terminal for sounding said oscillator and transferring a predetermined amount of energy other than that delivered to the oscillator; connections operative when energizing voltage is withdrawn by opening said first key switch, for restoring the open-key condition of said first circuit by current through said oscillator to produce a predetermined, relatively short decay period immediately after the voltage is withdrawn; a second circuit completed by said second key switch through said second terminal for sounding said oscillator and transferring a difierent, larger, predetermined amount of energy other than that delivered to said oscillator; connections operative when energizing voltage is withdrawn by opening said second key switch, for restoring the open-key condition of said second circuit by current through said oscillator to produce a second, relatively long decay period immediately after energizing voltage is withdrawn.

2. A combination according to claim 1 in which each of said energy transfer means includes a capacitor connected to change its condition of charge or discharge in one direction when its key switch is closed and in the opposite direction when voltage is withdrawn.

3. A combination according to claim-2 in which both capacitors are in branch circuits parallel with said oscillator and in charged condition when energizing voltage is present; said branches being in series with said oscillator when said key switches are open, to compel the capacitor charge to pass through said oscillator and energize it temporarily and with progressively decreasing potential.

4. An electronic organ comprising, in combination: a single set of oscillators according to claim 1; there being only one oscillator for each musical pitch within the range of the instrument; two sets of playing keys and key switches; and player-controlled stop switch means for connecting all the keys of either set to the first terminals or to the second terminals of the corresponding oscil lators.

5. A combination according to claim 2 in which a diode isolates the capacitor of said second energy-transfer circuit from said oscillator, when energizing voltage is supplied to said first circuit only; whereby energizing of said second circuit causes the capacitors of both the first and the second circuits to experience an energy transfer.

6. An electronic organ comprising, in combination: a series of independently tuned LC oscillators; each oscillator generating signal of predetermined wave shape corresponding to the signal to be translated into sound; there being a separate independent oscillator for each semi-tone within the range of the instrument; a source "of DC. activating voltage; player controlled key-switch means for delivering D.C. activating voltage to preselectred oscillators only as long a the player holds the key *down; each oscillator having its own characteristic decay rate in its oscillation when activating voltage is cut oif by opening the key switch; ancillary energy transfer means for each oscillator, for rendering any one of a plurality of different amounts of energy available to continue the activating voltage'on a decreasing scale after source voltage is cut ofi? by opening the key switch; and quick-adjustable on-and-otf stop switch means accesible to the player for selecting the amount of energy to be supplied from sai'd'transfer means; said transfer means comprising a capacitance connected to experience an energy transfer in one direction when a key switch is closed, and in the other direction when a key switch is opened; said stop switch means operating to vary the time rate at which said capacitance is restored to openkey condition.

7. An organ according to claim 1 in which the variation in time rate is secured by varying the resistance through which current flows during return to open-key condition.

8. In an electronic organ, in combination: tone-producing means including a normally inactive audio-frequency oscillator having the frequency of a musical note to be produced; loud speaker means for translating the vibrations of said tone-producing means into sound waves; said tone-producing means having predetermined characteristic attack and decay periods; said tone-producing means having a first and second terminal; a

first'anda second keyswitch for delivering energizing voltage to sound .said tone-producing means; a first circuit completed by said first .key switch through said first terminal for soundingsaid tone-producing means; a second circuit completed by said second key switch through said second terminal for sounding said tone-producing means and transferring a predetermined amount of energy other than that delivered to said tone-producing means;

and connections operative when energizing voltage is withdrawn by opening said second key switch, for restoring the open-key condition of said second circuit'by current through said tone-producing means to prolong the predetermined decay period of said tone-producing means and produce a slower dying away of the signal.

Reterences Cited in the file of this patent I UNITED STATES PATENTS UNITED STATES PA'I EN T OFFICE CERTIFICATE OF CORRECTION Patent No. 2,924,137

February 9 1960 Richard H. Peterson line 4, for as long a the" read line 21, for the claim reference numera as long as for a first and sec flrst and a second l "1" read 0nd" read a I Signed and sealed this of August 1960 (SEAL) Attest:

KARL H, AXLINE ROBERT C. WATSON Attesting Ofiicer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No 2, 924 137 February 9, 1960 Richard H'. Peterson It is hereby certified that error appears in the-printed of the above numbered patent requiring correction and that the Patent should specification read as corrected below.

said Letters Column 7, line 4, for "as long a the" read as long as the line 21, for the claim reference numeral "-1" read column 8 line 2-, for a first and second" read a first and a second Signed and sealed this znj 'day of August 1960 (SEAL) Attest:

KARL H AXLINE I ROBERT C. WATSON Attesting Officer Commissioner of Patents 

